Out of Eden

On the east coast of Scotland, an innovative project is seeking to show that tropical shrimp can be grown – at commercial scale – in colder climes.

Growing king prawns in the UK for same-day delivery to the local market is an appealing alternative to shipping them from halfway around the world. The obvious drawback, however, is that L.vannamei is a tropical species and – spoiler alert – Britain is far from being a tropical country.

Even a comparatively pleasant summer day in these climes falls short of what these shrimp need to thrive, so to grow them, an artificially warmed environment is required. That presents a problem when energy prices are high and likely to remain so – but it is a problem to which Andrew Whiston, founder of Rastech, believes he has found a solution.

Rastech’s experimental farm site is based at the St Andrews University Eden Campus at Guardbridge, in Fife, on Scotland’s east coast.

It is situated on land reclaimed from the sea over the years with waste dumped from the now defunct paper mill – which means that several feet below ground level there is a protective membrane, shielding a variety of potentially hazardous waste materials. It means that potential uses of the site are limited, but the Rastech site does not need deep foundations and its water is drawn from the North Sea, not groundwater.

The Eden Campus is being developed by the university as a centre for innovation and technology, and Rastech is the first tenant, although the Eden Mill distillery is a near neighbour.

Solar panels, Eden campus, St Andrews

The Rastech team’s solution to the energy problem is twofold. First, the farm is heated and powered entirely by renewable energy. It is not on the main energy grid – instead, its power sources are a solar panel array run by the university and a biomass boiler run on woodchips. The CO₂ waste from the boiler is catalysed to create an alkali supplement for the shrimp farm, as part of the project’s “circular economy” ethos.

As Whiston puts it: “We’re circularising somebody else’s waste and using it in a way that benefits us.”

Running off-grid not only helps to cut costs, but also shows that the farm’s model could work in remote locations – either on the Scottish coast or for example in Africa – where there is little or no access to mains electricity.

The second element involves ensuring that as little heat as possible is wasted. For this, the Rastech team drew from the experience of Fife’s fruit growing sector, which uses polytunnels to keep its crop safe while taking advantage of the region’s long hours of summer sunshine.

Rastech farm

These polytunnels were the inspiration for the design of the Rastech’s insulated unit, which looks something like a larger version of a Nissen hut from the Second World War.

It is basically a 30-metre polytunnel with insulation. Fibre glass – the material typically used for insulating houses – would have been too heavy for the structure, but instead a polyester-based material, like the insulation found inside a duvet, was used. It is derived from recycled, single use plastic bottles.

And it works. Whiston says: “This winter it was -7C outside, with snow on the roof, but it was 32C inside.”

Shrimp farming can be green
Inside, there are two separate sections. The first is a functioning RAS (recirculating aquaculture system) unit – or rather, two units running in parallel with separate filter systems.

This, when Fish Farmer visited, housed the farm’s shrimp in two sets of four tanks each. The parallel set-up means that research and development can be carried out on one set while the other acts as a control group.

The second and larger section will operate on a near-commercial scale, with five tanks, each with a capacity of 23,000 litres, giving a total capacity of 115,000 compared with the 8,000 litres capacity of the R&D unit.

R&D tanks

The larger tanks are built from low-carbon concrete, a material that preserves heat much better than the plastic tanks in a typical RAS system. At the time of our visit, the tanks were being prepared to accept their new inhabitants.

The shrimp at the Guardbridge site are imported as juveniles from the United States. This is a more biosecure source than bringing them in from one of the big shrimp farming regions in the tropics, but even so the supply could potentially be interrupted, either by a disease problem leading to a ban by the UK authorities, or major weather events such as hurricanes affecting the southern US.

The plan, therefore, is to move – at some point next year – to obtaining broodstock and producing homegrown juveniles, for Rastech and for other UK producers. This would create more security for the UK industry, Whiston believes.

Water from the farm is drawn from the Eden estuary, which is a site of special scientific interest. Ironically – or sadly – it is too dirty to farm L.vannamei so it has to be filtered before use. In fact, says Whiston, the filtered effluent from the shrimp farm is actually much cleaner than the water in the estuary.

Samphire grown using hydroponics

Solid waste from the tanks is filtered out and the nutrients in the liquid waste are used to grow salt-tolerant crops. In this case, Rastech is growing samphire, a succulent seashore plant often used as a garnish for seafood.

Will UK grown shrimp be cheaper? No – but it will be much more environmentally friendly, Whiston says.

Much the world’s shrimp production in coastal ponds contributes to marine pollution, with minimally filtered effluent returned to the sea, degradation of local ecosystems like mangrove forests and excessive use of antibiotics. And that’s without calculating the airmiles.

He stresses: “If they [pond farming producers] had to farm to our standards, we would not be more expensive.

“Our shrimp will incur NO airmiles and NO antibiotics, ever.”

Juvenile shrimp

The Guardbridge site is currently operating as a research and proof of concept project, but it could easily be expanded to a fully commercial scale, Whiston believes.

Rastech, as well as producing its own shrimp for sale, could operate as a hatchery for other producers and as a supplier, offering RAS shrimp farms on what would be more or less a “plug and play” basis. To achieve these ambitions, however, the company will need outside investment – so far it has been self-funded, but scaling up will require more capital.

So far, what Rastech has shown is that shrimp farming in the UK is more than possible, and also that it can be done in a sustainable manner.
Even the site’s office unit is recycled – it was originally part of a refrigerated lorry operated by a national supermarket chain, and it could also function as a container for shipping out RAS components to other would-be farmers.

As Whiston puts it: “We are trying to prove that environmentally friendly production can be profitable!”

Click here to see Fish Farmer’s video interview with Dr Andrew Whiston:
https://www.youtube.com/watch?v=JBBEucFQLO4